Separation of materials



Feb. 11, 1958 E. R. UMNEY 2,822,923

SEPARATION OF MATERIALS Filed April 30, 1953 Inventor LAURIE .15. R. uMA/Ey A ttorrzey' United States Patent SEPARATION OF MATERIALS Laurie Edward Richard Umney, Gnildford, England,

' assignor to Vokes Limited, Guildford, England Application April 30, 1953, Serial No. 352,209

Claims priority, application Great Britain June 27, 1952 1 Claim. (21. 209-139 This invention concerns an improved method and apparatus for separating one of two or more dissimilar materials from a mixture.

It is often necessary to separate a wanted product from a mixture of that product and a waste product which has different characteristics of air resistance or density. For example in the tobacco industry it is necessary to separate shredded leaf from a mixture of leaf and stalk.

In the method according to the invention a mixture of materials is continuously conveyed into a zone traversed by an upwardly flowing air stream of sufficient intensity to entrain a lighter or more air-resistant component of the mixture and the airstream with the entrained component is subjected to a process of centrifugal or other separation process to remove the entrained component before being returned to the upwardly traversed zone.

In one preferred method according to the invention a proportion of the airstream is by-passed on its route to the upwardly traversed zone through a dust recovery filter in order to keep the proportion of unwanted dust at a low level in the continuously circulating airstream.

Apparatus according to the invention comprises a jigging or other conveyor for the transport of a mixture of materials into a zone defined between air ducts arranged opposite one another below and above the plane of the conveyor, a perforated section of the conveyor extending at least over this zone, a vertical leg in the upper air duct led to a centrifugal separator the material outlet of which is sealed from atmosphere by a rotary or like valve, and a fan to induce airflow into the airduct below the conveyor and through the vertical leg and centrifugal separator back to the fan in a continuous circulation.

A preferred form of apparatus includes a bag type dust recovery filter which is connected between the outlet and inlet of the fan by ducts allowing a proportion of the air stream to be continuously by-passed from the main flow.

The above and other parts of the invention are embodied in a preferred method and apparatus designed for the separation of shredded tobacco leaf from a mixture of leaf and stalk, which will now be described in some detail by way of example with reference to the accompanying drawings in which:

Fig. 1 is a diagrammatic side elevation of a separator in part section.

Fig. 2 is a plan view of the separator of Fig. 1.

A mixture of tobacco leaf shreds Whose area varies between a fraction of a square inch and several square inches and of relatively dense stalks from which the leaf has been shredded is fed at the rate of about 1000 lbs/hour on to a jigging conveyor 1 some three feet wide.

The action of the jigging conveyor causes the leaf shreds to lie with the plane of their largest area flat on the base of the conveyor.

The conveyor has a section 2 some twelve inches long by twenty seven inches wide which is extensively perforated.

An airduct 3 having an open mouth 4 of similar dimensions is arranged immediately beneath the perforated section 2 of the conveyor, and a further air duct 5 with an open mouth 6 of similar dimensions is arranged immediately above the perforated section 2.

The upper air duct has a vertical leg several feet high and is connected at its upper end to a curved corner piece 7 which is fitted with curved baflies or divided into several sections 7a, 7b, 7c of reduced cross-sectional area to ensure smooth and rapid flow.

A short horizontal section 8 of smaller cross-section than the vertical leg of the duct leads from the corner piece into the inlet of a centrifugal separator 9.

The material outlet 10 of this separator is fitted with a continuously rotating, power-driven rotary valve 11 to seal it from the outer atmosphere.

A further section of ducting 12 leads from the central outlet 13 of the centrifugal separator to the inlet eye 14 of a draught inducing fan 15.

The outlet 16 of the fan is connected to the first mentioned air duct 3 whose open mouth lies beneath the conveyor.

A branch 17 from the outlet duct 3 is connected to the inlet of a bag type dust recovery filter 18 and the clean air outlet 19 of the filter is connected back to the ducting 12 between the separator 9 and the inlet to the fan 15.

In this particular form of apparatus the fan is driven by a five to six horse power motor 20 and has a capacity of about 2500 C. M. F.

About 400 C. F. M. of the air delivered by the fan is by-passed through the dust recovery filter 18.

It is desirable that the mouth 6 of the duct 5 arranged above the conveyor be provided with an arcuate section bulge 21 at its trailing edge in order to accommodate eddies set up at this point.

In operation the mixed leaf and stalk is continuously fed onto the perforated section 2 of the conveyor 1 where it is subjected to the upwardly flowing air-stream from the lower to the upper air duct. The leaf shreds, which are lighter and have greater air resistance are picked up by the air current and swept into the vertical leg of the upper duct. Any pieces of stalk which may happen to be lifted with pieces of leaf fall back under gravity onto the conveyor as the pieces of leaf are whirled and twisted in the ascending air stream. The greater proportion of stalk pieces are not effectively lifted from the perforated section of the conveyor and are transported away for disposal.

The pieces of leaf entrained in the air stream flow around the corner piece 7, through the short horizontal section 8 and are separated out in the centrifugal separator 9, from which they are continuously extracted as the rotary valve 11 revolves and fed down a shoot 22 on to a conveyor 23.

The air stream, which now only contains a proportion of dust, enters the eye of the fan 15 and is re-circulated through the apparatus.

A small proportion of the air is continuously circulated through the dust recovery filter 13 to keep the dust content at unobjectionable proportions.

It will be understood that the invention is not restricted to the details of the specific embodiment described which may be varied Without departing from the appended claim.

I claim:

An apparatus for separating one of several dissimilar materials from a mixture, comprising a conveyor for Patented Feb. 11, 1958 transporting a mixture of materials and having a perforated section, a continuous duct system that is closed throughout except for ends disposed immediately above and below the perforated section of said conveyor, a single fan in said duct system to induce airflow into the duct below the conveyor and up into the duct above the conveyor to draw certain of the materials into said duct system, a centrifugal separator for separating the material from the air stream in the duct system, and a bag type dust recovery filter connected to said duct system by an outlet between the outlet of said separator and the inlet of the fan and by an inlet on the outlet side of said fan to continuously by-pass a proportion of the airflow from the main flow to continuously remove a portion of the dust from the air stream.

UNITED STATES PATENTS Sargent Dec. 17, 1907 Lehrack et a1. July 13, 1915 Stebbins July 16, 1929 Lorentz Apr. 8, 1930 Dorfan Aug. 2, 1932 Harlow July 25, 1944 Erisman Oct. 26, 1948 Eissmann Jan. 26, 1954 FOREIGN PATENTS Austria Aug. 25, 1952 Germany Dec. 2, 1937 

